1. Field of the Invention
The invention relates to a method for transmitting data and on interfaces for transmitting or receiving data, by means of a predetermined sequence of a first state and a second state, distinguishable from each other, and relates in particular to a voltage controller with an interface in a motor vehicle.
2. Prior Art
From German Patent Disclosure DE 35 06 118, a method for transmitting data over a data line is already known, in which a sequence of first and second states, distinguishable from one another, are transmitted over the data line. These states then represent a high bit or a low bit.
It is an object of the present invention to provide an improved method of transmitting data of the above-described kind.
It is another object of the present invention to provide improved interfaces for transmitting and receiving data according to the method of the invention.
The method and interfaces according to the invention have the advantage over the prior art that a third state is provided, which is utilized for transmitting a synchronization signal. The synchronization can therefore be generated in the data stations involved, and can be imparted to the other stations involved over the data line. As a result, it is possible for only one of the data stations involved internally to have the means for generating a synchronization signal, while the other stations need not have any such means.
It is especially advantageous that work can also be done with two voltage levels. This advantage is attained in that both the synchronization pulses and the other two items of information, such as a zero datum and a one datum are embodied by pulses of different signal lengths. Advantageously, the pulses that include the two items of information begin simultaneously with the respective synchronization pulse. The transmission is advantageously effected between a first data station and a second station, which communicate with one another through a transmission line. It is especially advantageous that the system can also be used when there are a plurality of receivers, and that a transmission protocol is produced.
Advantageous refinements of and improvements to the method and the interface of the invention are disclosed. The synchronization signal becomes especially simple if it comprises putting the data line into the third state for a predetermined minimum time. The receiving station can then be synchronized to the signal edge that indicates the end of the third state. It is then simple to write in a high bit or a low bit, by writing in, after the synchronization signal, whether the data line is in the first or the second state. It is also advantageous in this regard that the length of the synchronization signal or of the high bit or a low bit does not matter, as long as they each exceed a predetermined minimum time that is needed for reliable detection of the respective state on the data line. The various states on the data line are especially simply embodied by different voltage levels.
Using the interfaces of the invention in the method for data transmission of the invention can advantageously be done in the form of using a bit-synchronized interface in the motor vehicle. An especially advantageous application of the interface is the communication between the voltage controller and the on-board electrical system of a motor vehicle. Communication between the voltage controller and the microcomputer of the digital engine electronics as a component of the engine control unit is likewise advantageously possible.